Electroless nickel,cobalt and nickel-cobalt alloy plating from fluoborates sources



United States Patent 9 Claims ABSTRACT OF THE DISCLOSURE The invention hereinafter described relates to novel methods of autocatalytic or commonly called electroless plating of nickel, cobalt and their common alloys, and further employs fluoborate solutions and methods for their use in producing nickel, cobalt and alloy deposits by non-electrolytic means, such deposits having the quali ties of superior corrosion resistance, zero-to-compressive internal stresses and excellent hardenability characteristics under ordinary heat-treating or accelerated aging processes.

This is a continuation-in-part of my patent specification Serial No. 476,183, filed July 30, 1965, now Patent Number 3,378,400 issued Apr. 16, 1968.

Another object of this invention is to provide additional stress relief, ductility and activation within the structure of the nickel, cobalt or nickel-cobalt-alloy deposits by electroless plating in a solution whose total metallic source consists of nickel fluoborate, cobalt fluoborate, or a combination thereof.

A further object of this invention is to provide versatile and very adaptable electroless nickel, cobalt and alloy plating baths by including the fluoborate ion in electroless plating solutions which are made up from conventional salts of nickel and cobalt such as nickel sulfate, cobalt sulfate, nickel chloride, cobalt chloride, etc., such fluobo rate ion being included by its addition to the baths in the form of fluoboric acid or any of the derivatives of fluoboric acid, i.e., nickel fluoborate, calcium fluoborate, sodium fluoborate, potassium fluoborate, etc.

It is a further object of this invention to provide metallic coatings which are relatively soft and very receptive to subsequent plating deposits of chromium, brass, palladium, rhodium, nickel, etc., by chemically plating a deposit from nickel fluoborate, cobalt fluoborate or a combination thereof, without the addition of fluoboratetype, non-metallic derivatives.

Yet another object of this invention is to deposit metallic coatings of such potential adhesion and zero-to-compressive internal stress that they may be applied directly to aluminum and magnesium surfaces without extensive pre-treatment and without the necessity of depositing other coatings between the aluminum or magnesium substrate and the nickel, cobalt or alloy coating being deposited from the solutions of the invention.

Another object of this invention is to provide metallic coatings possessing such properties of adherence and voidfreeness that they may be applied to the surfaces of sensitized non-metallic materials such as ceramics, glass, rubber, epoxies, phenolics, acrylics, vinyls, polypropylenes, polyesters and other normally inert materials without the acquisition through such coating buildup of cracks and voids due to tensile stresses inherited from the stressed substrate.

Yet another object of this invention is to provide a number, of autocatalytic or electroless plating solutions which will deposit nickel, cobalt or nickel-cobalt-alloy coatings upon the surfaces of metallic and non-metallic materials at a buildup rate within the range of .0001 and .0015 inch per hour of plating time, such deposition rate being dependent upon, and controlled by, temperature, agitation rate, pH and chemical concentrations, such deposited coating having a Rockwell C hardness in the range of 32 to 45 as plated, and capable of a hardness increase in the range of 25% to 35% over the asplated condition by being heated to a temperature range within 500 and 800 F., allowing to dwell at this temperature for 3 to 6 hours and cooled in air to ambient temperature. Hardnesses within the above ranges may also be obtained by accelerated aging, i.e., heating the as-plated coatings to a temperature within the range of 180 to 280 F., maintaining this temperature for a period of 8 to 16 hours, and cooling in air to ambient temperature.

A further object of this invention is to provide fluoboric acid or fluoborate addition agents for use in electroless nickel, cobalt or alloy plating solutions, such addition agents being buffered, if necessary, to a pH in a range suitable for use in raising or lowering the acidity or alkalinity of the plating solution and having the functions of enhancing ductility, grain refinement and appearance of the metallic coatings as well as accelerating the rate of deposit and providing pH control of the plating solution.

In general, this invention relates to a number of novel and unique solutions for use in the electroless deposition of nickel, cobalt or nickel cobalt alloys and these baths comprise between about 0.1 and 35.0 oz./gal. of nickel and/or cobalt fluoborate, 0.05 to 35.0 oz./ gal. of addition agents from the group consisting of fluoboric acid or its fluoborate derivatives, i.e., ammonium fluoborate, sodium fluoborate, potassium fluoborate, etc., 0.1 to 5 oz./gal. sodium citrate, 0.1 to 5 oz./gallon sodium acetate and 0.2 to 8 oz./gallon sodium hypophosphite. The present invention also relates to the method of depositing metallic coatings through use of the above materials from solutions in which the temperature is maintained within the range of 40 F. and 210 F., the pH between 0.5 and 14.5 and the metallic content within the range of 0.05 and 15.0 oz./ gallon.

Although the number of various and different operable plating solutions made possible by the use of fluoboric acid and its many fluoborate derivatives are virtually impossible to list within the pages of this specification, a few of the more common and typical solutions are as follows:

The fluoborate bath (nickel) Oz./ gallon Nickel fluoborate 0.1-35.0 Sodium citrate 0.1-5.0 Sodium acetate 0.1-5.0 Sodium hypophosphite 0.2-8.0

The fluoborate bath (cobalt) Cobalt fluoborate 0.1-35.0 Sodium citrate 0.1-5.0 Sodium acetate 0.1 5.0 Sodium hypophosphite 0.28.0

The fluoborate bath (nickel-cobalt alloy) Nickel fluoborate-l-cobalt fluoborate 1 0.1-35.0 Sodium citrate 0.1-5.0 Sodium acetate 0.1-5 .0 Sodium hypophosphite 0.2-8.0

1 Any ratio.

1 Any ratio. N'rn.-The nickel chloride salt may be mixed with or substituted for the sulfate.

The sulfate-fluobonate bath (cobalt) Cobalt fluoborate-l-cobalt sulfate 1 0.1-35.0 Sodium citrate 0.1-5.0 Sodium acetate 0.1-5.0 Sodium hypophosphite 0.2-8.0

1 Any ratio. NOTE.--Tlle cobalt chloride salt may be mixed with or substituted for the sulfate.

The sulfate-fluoborate bath (nickel-cobalt alloy) Nickel fluoborate-i-cobalt sulfate 1 0.1-35.0

Sodium citrate 0.1-5.0

Sodium acetate 0.1-5.0

Sodium hypophosphite 0.2-8.0

1 Any ratio.

Nora-The cobalt chloride salt may be mixed with or substituted for the sulfate.

The nickel bath (ammonium fluoborate added) Nickel sulfate 0.1-35 .0 Sodium citrate 0.1-5.0 Sodium acetate 0.1-5 .0 Ammonium fluoborate 0.1-35.0

No'ru.'lhe nickel salt may be mixed with or substituted for the sulfate.

The cobalt bath (ammonium fluoborate added) Cobalt sulfate 0.1-35.0 Sodium citrate 0.1-5.0 Sodium acetate 0.1-5.0 Ammonium fluoborate 0.1-35 .0

No'rn.The cobalt chloride salt may be mixed with or substituted for the sulfate.

Sodium, potassium, calcium, or other fluoborate, or fluoboric acid may be used in the foregoing baths of the invention without departing from the scope and spirit of this specification.

The ammonium, calcium or potassium salts of citrate, acetate or hypophosphite may be substituted for the sodium salt in all of the claimed solutions of the invention without departing from the purpose or scope thereof.

While a complete embodiment of the invention has been disclosed, it will be appreciated that modification of this particular embodiment of the invention may be resorted to without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. A solution for use in electroless nickel, cobalt or nickel-cobalt-alloy plating and comprising between 0.1 to 35.0 oz./gallon of one or more materials from the group consisting of nickel and cobalt fluoborate sources, between 0.1 and 5.0 oz./gallon sodium citrate, 0.1 to 5.0 oz./gallon sodium acetate and 0.2 to 8.0 oz./gallon sodium hypophosphite.

2. A solution for use in electroless nickel, cobalt or nickel-cobalt-alloy plating and comprising between 0.1 and 35.0 oz./gallon of one or more materials from the group consisting of nickel sulfate, cobalt sulfate, nickel chloride and nickel chloride between 0.1 and 5.0 oz./ gallon sodium citrate, 0.1 and 5.0 oz./gallon sodium acetate, between 0.2 to 8.0 oz./ gallon sodium hypophosphite and between 0.005 and 50.0 oz./gallon sodium fluoroborate.

3. A solution for use in electroless nickel, cobalt or nickel-cobalt-alloy plating and comprising between 0.1 and 35.0 oz./gallon of one or more materials from the group consisting of nickel sulfate, cobalt sulfate, nickel chloride and nickel chloride between 0.1 and 5.0 oz./ gallon sodium citrate, 0.1 and 5.0 oz./gallon sodium acetate, between 0.2 to 8.0 oz./gallon sodium hypophosphite and between 0.005 and 50.0 oz./gallon calcium fiuoborate.

4. A solution for use in electroless nickel, cobalt or nickel-cobalt-alloy plating and comprising between 0.1 and 35.0 oz./ gallon of one or more materials from the group consisting of nickel sulfate, cobalt sulfate, nickel chloride and cobalt chloride between 0.1 and 5.0 oz./ gallon sodium citrate, 0.1 and 5.0 oz./gallon sodium acetate, between 0.2 to 8.0 02/ gallon sodium hypophosphite and between 0.005 and 50.0 oz./gallon potassium fluoborate.

5. A solution for use in electroless nickel, cobalt or nickel-cobalt-alloy plating and comprising between 0.1 and 35:0 oz./gallon of one or more materials from the group consisting of nickel sulfate, cobalt sulfate, nickel chloride and cobalt chloride between 0.1 and 5.0 oz./ gallon sodium citrate, 0.1 and 5.0 oz./gallon sodium acetate, between 0.2 to 8.0 oz./ gallon sodium hypophosphite and between 0.005 and 50.0 oz./gallon ammonium fiuoborate.

6. A solution for use in electroless nickel, cobalt or nickel-cobalt-alloy plating and comprising between 0.1 and 35.0 oz./ gallon of one or more materials from the group consisting of nickel sulfate, cobalt sulfate, nickel chloride and cobalt chloride between 0.1 and 5.0 oz./ gallon sodium citrate, 0.1 and 5.0 oz./gallon sodium acetate, between 0.2 to 8.0 oz./gallon sodium hypophosphite and between 0.005 and 50.0 oz./gallon fluoboric acid.

7. A method of nickel, cobalt or nickel-cobalt-alloy electroless plating comprising the steps of forming a bath from about 0.1 to 35.0 oz./ gallon nickel fluoborate, cobalt fluoborate or a combination thereof, between 0.1 and 5.0 oz./ga1l0n sodium citrate, between 0.1 and 5.0 oz./gallon sodium acetate, between 0.2 to 8.0 oz./gallon sodium hypophosphite, immersing a metallic or nonmetallic article into the bath and causing nickel, cobalt or alloy plating to be deposited on the article while maintaining the solution at a temperature within the range of 40 F. and 210 F. and at a pH within the range of 0.5 to 14.5, and maintaining the strength of the solution by regular additions of its constituents.

8. A method of nickel, cobalt or nickel-cobalt-alloy plating comprising the steps of forming a bath from about 0.1 to 35.0 oz./gallon of one or more materials from the group consisting of nickel and cobalt sources of metallic ions, between 0.1 and 5.0 oz./gallon sodium citrate, between 0.1 and 5.0 oz./gallon sodium acetate, between 0.2 and 8.0 oz./ gallon sodium hypophosphite and between 0.005 and 50.0 oz./ gallon of one or more materials from the group consisting of fluoboric acid, ammonium fluoborate, calcium fluoborate, potassium fiuoborate and sodium fluoborate, immersing a metallic or nonmetallic article into the bath and causing nickel, cobalt or alloy plating to be deposited on the article while maintaining the solution at a temperature within the range of 40 F. and 210 F. and at a pH within the range of 0.5 to 14.5, and maintaining the strength of the bath by regular additions of its constituents.

9. A method of nickel, cobalt or nickel-cobalt-alloy plating comprising the steps of forming a bath from 0.1 to 35.0 oz./gallon of one or more materials from the group consisting of nickel and cobalt sources of metallic ions, between 0.1 and 5.0 oz./gallon sodium citrate, between 0.1 and 5.0 oz./ gallon sodium acetate, between 0.2 and 8.0 oz./gallon sodium hypophosphite and between 5 6 0.005 and 50.0 oz./-gallon of one or more materials from References Cited the group consisting of fluoboric acid, ammonium fluo- UNITED STATES PATENTS borate, calcium fluoborate, potassium fluoborate and sodium fluoborate which have been buffered by alkaline or gfig igg'g 'g ist 7:3 acid reagents to a pH within the range necessary to control 5 3378400 4/1968 Sickles the pH of the solution within desired limits, immersing u a metallic or non-metallic article into the bath and caus- OTHER REFERENCES ing nickel, cobalt or alloy plating to be deposited on the Serota, Metal Finishing, August 1962, pp. 64, 65.

article while maintaining the solution at a temperature RALPH S KENDALL P E within the range of 40 F. and 210 F. and at a pH within 10 mmme" the range of 0.5 to 14.5, and maintaining the strength of US. Cl. X.R. the bath by regular additions of its constituents. 1061; 117-47, 160 

